Scalp contacting bioelectrode



Sept. 30, 1969 J. A. R. KATER 3,469,577

SCALP CONTACTING BIOELECTRODE Filed March 2, 1967 3e 4o 36 4o 48 5 3 I 4\50 I, A I

60 JIIOHN A. R. KATER Fla. 7 INVENTOR.

ATTORNEY United States Patent 3,469,577 SCALP CONTACTING BIOELECTRODEJohn A. R. Kater, Diamond Bar, Calif., assignor to Beckman Instruments,Inc., a corporation of California Filed Mar. 2, 1967, Ser. No. 620,011Int. Cl. A61b /04; A61m 35/00 U.S. Cl. 128-21 9 Claims ABSTRACT OF THEDISCLOSURE A bioelectrode for attachment to the scalp of a subjectwithout removing hair from the scalp. The bioelectrode is generally inthe form of a ring, having a slot therein so that hair on the scalp canbe readily passed through the slot into the opening in the ring. Meansare provided for securing the ring to the air so that the ring is heldin physical contact with the scalp.

This invention relates to means for establishing conductive contact withthe scalp of a living subject and, more particularly, to a bioelectrodeand method for applying the same to the scalp of a subject forelectroencephalographic potential measurements.

In electroencephalography (EEG) a bioelectrode is attached to the scalpof the subject to establish conductive contact with the scalp in orderto measure brain waves. Present techniques for attaching such electrodesto the scalp include glueing the electrode to the scalp with cement,collodion or other adhesives, the use of low melting paraffin andspecial head frames to hold the electrode to the scalp under lightpressure. These methods are messy and cumbersome, the main obstaclebeing the hair on the scalp. Heretofore, the only alternative to theabove method for applying electrodes to the scalp was the shaving of thescalp to remove the hair so that the electrodes could be applieddirectly to the scalp in a conventional manner utilizing thin adhesivediscs. However, for obvious reasons many subjects do not care to havetheir heads shaven for electrode attachment purposes.

It is, therefore, the principal object of the present invention toprovide improved method and means for establishing electrical contactwith the scalp of a subject.

Another object of the invention is to provide an improved bioelectrodefor attaching to the scalp of a subject without removing the hair fromthe scalp or requiring the use of cements, adhesives, paraflin or thelike.

According to the principal aspect of the present invention, there isprovided a bioelectrode having a central opening therethrough which ispositioned in physical contact with the scalp of the subject with hairfrom the scalp passing through said opening. The opening in thebioelectrode is then filled with an electrolyte and the bioelectrodesecured firmly to the scalp by either tying the hair passing through theopening in the bioelectrode into a knot above the bioelectrode orapplying a cap to the bioelectrode clamping the hair between the cap andthe bioelectrode. Thus, the hair of the subject is utilized as an anchorfor the bioelectrode establishing firm contact between the bioelectrodeand the scalp thereby reducing possible motion artifacts. Consequently,no hair need be removed from the scalp of the subject, nor are cements,adhesives or head frames required for maintaining the bioelectrode infirm contact with the scalp.

Other objects, aspects and advantages will become apparent from thefollowing description taken in connection with the accompanying drawingswherein:

FIG. 1 is a perspective view of one form of the bioelectrode of theinvention.

FIG. 2 is a perspective view showing the bioelectrode of FIG. 1 securedto the scalp of a subject in accordance with the present invention;

FIG. 3 is a cross-sectional view of another form of the bioelectrode ofthe invention;

FIG. 4 is a perspective view of still a further form of the bioelectrodeof the invention which comprises a circular member and a cap which areshown unassembled;

FIG. 5 is a cross-sectional view of the bioelectrode shown in FIG. 4with the cap and circular member assembled;

FIG. 6 is a cross-sectional view of the bioelectrode illustrated in FIG.5 shown attached to the scalp of a subject; and

FIG. 7 is a cross-sectional view of still a further form of thebioelectrode of the present invention.

Referring now to the drawings in detail, FIGS. 1 and 2 illustrate oneform of the bioelectrode of the invention, generally designated bynumeral 10. The bioelectrode comprises a generally circular member 12having an opening 14 extending vertically through the membrane formingan electrolyte reservoir. The member 12 is preferably formed from silverfoil which is flared out at the lower portion thereof to provide aflange 16 for contacting the scalp of a subject. The silver circularmember 12 is chloridized so as to provide a silver chloride coating onthe wall of the opening 14 which is the conductive element of thebioelectrode. An insulated wire 18 is connected to the element 12 forelectrical connection to an electroencephalograph. An insulating coating20 is provided on the outer surface of the element 12.

In accordance with the principal feature of the present invention, thebioelectrode is secured to the scalp 21 of a living subject without theuse of cements, adhesives, paraffin or head frame, and furthermorewithout the requirement of shaving the scalp of the subject, by passinga portion 22 of the hair of the scalp through the opening 14 in thebioelectrode in a fashion as shown in FIG. 2. The hair is readily passedthrough the opening 14 by providing a slot 23 in the member 12 whichextends from the Opening 14 to the edge of the insulation layer 20. Byproviding such a slot, the hair need not be threaded through the opening14 but need only be passed laterally through the slot 23 into theopening 14 when positioning the bioelectrode on the scalp. After thebioelectrode is positioned on the scalp, electrolyte is inserted intothe opening 14 to provide an electrolytic path between the silverchloride coating on the member 12 and the scalp. Thereafter, the hairpassing through the opening 14 is tied into a knot 24 at the upperportion of the bioelectrode firmly securing the bioelectrode to thescalp.

FIG. 3 shows an additional form of the bioelectrode of the invention,generally designated by numeral 25, which has a similar configuration tothe electrode shown in FIG. 1. The bioelectrode 25 includes a circularmember 26 formed of a non-conductive material such as plastic havingessentially the same configuration as the member 12 in FIG. 1. Anelectrode component 28, such as a silversilver chloride pellet asdescribed in US. Patent No. 3,111,478 is mounted on the wall of theopening 30 in the member 26. An insulated wire 32 is connected to theelectrode component 28 by any suitable means and passes outwardlythrough the nonconductive member 26 for connection to an externalcircuit. As seen in FIG. 3, the electrode component 28 is mounted remotefrom the bottom flanged end 34 of the bioelectrode so that motionartifacts are minimized. The bioelectrode 25 has a vetrical slottherein, not shown, similar to the slot 23 in FIG. 1 so that it may beattached to the scalp of a subject in the same manner as described abovein connection with bioelectrode 10.

An additional form of bioelectrode of the invention is illustrated inFIGS. 4 and 5 and generally designated by numeral 36. This bioelectrodecomprises a circular member or ring 38 and a cap 40. The ring 38 has acentral opening 42 therethrough and a slot 44 extending from the openingto the outer edge of the ring 38. The ring 38 is preferably formed ofsilver which has been chloridized to form a surface coating of silverchloride thus constituting the conductive element of the bioelectrode.The cap 40 is formed of an insulating material such as plastic and has aprojection 46 which, as best seen in FIG. 5, has a length less than theheight of the ring 38 so as to provide 'a portion of the opening 42 opento form a reservoir for receiving electrolyte. The projection 46 has adiameter essentially the same as that of the opening 42 so as toestablish a friction fit between the two elements when assembledtogether. An insulated wire 48 is suitably attached to the ring 38 forconnecting the ring to an external circuit.

In attaching the bioelectrode 36 to the scalp 21 of a subject, a portionof the hair of the subject is passed through the slot 44 into thepassage 42 and laid across the upper annular surface or end 50 of thebioelectrode as best seen in FIG. 6. The passage 42 is then partiallyfilled with an electrolyte. Thereafter, the cap 40 is frictionallyengaged into the opening 42 of the ring 38 so as to clamp the hairpassing through the passage 42 securely thereby firmly securing thebioelectrode to the scalp of the subject.

While the bioelectrode 36 is shown as employing a ring 38 formedentirely of the conductive material, it is understood that the ring 38could be formed of a nonconductive material with an electrode componentsuch as the component 28 illustrated in FIG. 3 mounted in the opening42. Also, the metallic ring 38 of the bioelectrode 36 may be coated withan insulating layer except on the wall of the opening 42.

A bioelectrode 56 is illustrated in FIG. 7 having the same configurationas the bioelectrode 36 except that the ring member 38 is formed entirelyof an insulating material and an electrode component 60 is mounted inthe cap 62 so as to be exposed to electrolyte in the passage 64 in thering '58. An insulated wire 66 is connected to the electrode component60 and extends through the cap 62 for connection to an external circuit.The ring 58 has a vertical slot therethrough, not shown, to facilitatethe passing of hair on the scalp through the passage 64 so as to securethe ring 58 to the scalp of a subject in the manner described above inconnection with bioelectrode 36.

According to another feature of the invention, one or more hairs arepulled from the scalp of the subject at the point where the electrolytereservoir of the bioelectrode overlies the scalp. This permitselectrolyte to fill the root cavity which results in the sourceimpedance being substantially reduced. When employing a bioelectrode ofthe type disclosed herein, a hair which passes through the opening inthe bioelectrode is pulled out of the scalp either before or afterfilling the electrolyte reservoir with electrolyte. It has been foundthat by this method the source impedance is reduced, thereby improvingthe performance of the bioelectrode. Although several embodiments of theinvention have been disclosed herein for purposes of illustration, itwill be understood that various changes can be made in the form,details, arrangements and proportions of the various parts in suchembodiments without departing from the spirit and scope of the inventionas defined by the appended claims.

What is claimed is:

1. A bioelectrode for attachment to the scalp of a subject withoutremoving hair from the scalp comprising:

a circular member having a central opening therethrough with an annularend of said member being adapted to physically contact the scalp;

at least a portion of the wall of said opening being conductive and saidopening being capable of containing an electrolyte for providing anelectrolytic path between said conductive portion and the scalp; saidmember having a slot extending from said opening to the outer edge ofsaid member whereby hair on .4 the scalp may be passed through said slotto said opening when said annular end of said member contacts the scalp;

lead wire means attached to said conductive portion for connection to anexternal circuit; and

securing means replaceably mounted on said circular member for rapidlyand firmly securing hair passing through said central opening to saidmember.

2. A bioelectrode as set forth in claim 1 wherein said securing meanscomprises a cap frictionally engaging the other annular end of saidcircular member.

3. A bioelectrode for attachment to the scalp of a subect withoutremoving hair from the scalp comprising:

a circular member formed of silver having a central opening therethroughwith an annular end of said member being adapted to physically contactthe scalp;

the wall of said central opening having a coating of silver chloridethereon and said opening being capable of containing an electrolyte forproviding an electrolytic path between said silver chloride coating andthe scalp;

said member having a slot extending from said opening to the outer edgeof said member whereby hair on the scalp may be passed through said slotto said opening when said annular end of said member contacts the scalp;and

lead wire means attached to said circular member for connection to anexternal circuit.

4. A bioelectrode for attachment to the scalp of a subject withoutremoving hair from the scalp comprising:

a circular member formed of nonconductive material having a centralopening therethrough for containing an electrolyte with an annular endof said member being adapted to physically contact the scalp;

said member having a slot extending from said opening to the outer edgeof said member whereby hair on the scalp may be passed through said slotto said opening when said annular end of said member contacts the scalp;

cap means frictionally engaging the other annular end of said member;

an electrode component mounted in said cap with a portion of saidcomponent being exposed to said opening in said member; and

lead wire means connected to said electrode component for connection toan external circuit.

5. A method of establishing conductive contact with the scalp of asubject without removing hair from the scalp comprising the steps of:

providing a circular member having an opening therethrough with at leasta portion of the wall of said opening being conductive;

placing an end of said member in physical contact with said scalp with aportion of the hair on the scalp passing through the opening in saidmember;

filling said opening with an electrolyte; and

thereafter firmly securing said member to the hair passing through saidopening.

6. A method as set forth in claim 5' wherein said member is secured tosaid hair by tying the hair in a knot at the other end of said member.

7. A method as set forth in claim 5 wherein said member is secured tosaid hair by frictionally engaging a cap on the other end of said memberwith the hair positioned between said cap and said other end.

8. A method of establishing conductive contact with the scalp of asubject without removing hair from the scalp comprising the steps of:

providing a circuit member formed of nonconductive material having anopening therethrough;

placing an end of said member in physical contact with said scalp with aportion of the hair on the scalp passing through the opening in saidmember and overlying the other end of said member;

filling said opening with an electrolyte;

providing a cap carrying an electrode component; and

frictionally engaging said cap on the other end of said member to clampsaid hair therebetween with said electrode component contacting theelectrolyte in said opening.

9. A method of establishing conductive contact with the skin of asubject comprising the steps of:

providing a bioelectrode comprising a body having a reservoir filledwith electrolyte opening at one face of the body with a conductivemember in said reservoir;

pulling at least one hair from the skin of the subject to reduce thesource impedance; and

applying said bioelectrode to the skin with said reservoir overlying thepoint where said hair was removed.

References Cited UNITED STATES PATENTS 2,887,112 5/1959 Smith 128-4173,157,181 11/1964 McCarty 128404 WILLIAM E. KAMM, Primary Examiner U.S.Cl. X.R. 128-417

